1. Field of the Invention
The present invention relates a storage system and a data movement method that can move data among a plurality of types of storage areas.
2. Description of the Related Art
The storage system is composed of a large number of disk drives arranged in the form of an array, and provides storage area based on RAID (Redundant Array of Independent Disks). A logical volume, which is the logical storage area, is formed in the physical storage area possessed by the disk drives. A server or another host device can access the desired volume, and read and write data by issuing a prescribed command to the storage system.
A very large amount of data accumulates in the storage system in accordance with the operation of the storage system. In view of the above, a so-called data migration technique has been proposed (Japanese Laid-open Patent Application 2004-295457) whereby data with a high frequency of use is stored in a high-speed disk drive, and data with a low frequency of use is stored in a low-speed disk drive.
In the prior art cited in the reference, hierarchical storage control (data migration) based on the characteristics of the file is implemented in the storage device without reliance upon a host device. In the referenced technique, storage resources are effectively used by moving data exclusively from the vantage point of the storage device.
When the size of the storage system is relatively small, for example, and there is adequate communication between the storage device manager (hereinafter referred to as “storage manager”) and the host device manager (hereinafter referred to as “host manager”), no particular problems occur if data is moved with consideration given exclusively to the situation of the storage device.
In the contrasting case of a large storage system that includes a plurality of host devices and a plurality of storage devices, the duty allotment of the host manager and the storage manager increase. As a result, it is more difficult to manage in advance intentions with regard to data migration between the host manager and the storage manager.
When data is moved from one disk to another disk on the exclusive basis of the situation and vantage point of the storage device, as in the above-cited reference, the data movement would be welcomed by the storage manager, but not necessarily so by the host manager. This is because the intention of the host manager is not considered in any way in this data movement.
Assume a model of ordinary ILM (Information Lifecycle Management) in which data access frequency is high in the first stage of generation, the access frequency decreases with the passage of time, and the data is finally not accessed at all. In such a model, data is stored in a high-speed disk in the first stage of data generation, for example, and when the access frequency decreases, the data is moved from the high-speed disk to a low-speed disk; and the data is ultimately backed up to a tape device or the like and used offsite.
However, not all data matches such a standard model. Web server access logs, mail server transmission logs, and other such data require high-speed access during the generation thereof, for example, and the access frequency decreases with the passage of time, but inspection and monitoring may be carried out at regular or irregular intervals.
For instance, the access log and the transmission log are used to inspect the security of the server, and to confirm, among other things, whether trade secrets have leaked by the e-mail transmitted from inside the company to the outside. The host manager prefers to have the access log and the transmission log to be stored on a high-speed disk in order to complete such an inspection in a short time. However, the storage manager, which has not been informed of the inspection schedule, moves the access log and the transmission log to a lower speed disk. As a result, data that requires high-speed access is moved to a low-speed disk, contrary to the expectations of the host manager, and the convenience of the storage system decreases.